Chipping knives for chipping head assemblies

ABSTRACT

A chipping knife mountable on a head rotatable about an axis at right angles to a longitudinal axis of a log to be chipped, the knife having flat bottomed grooves formed in an advance face which open into a bevelled surface so as to provide advance and trailing cutting edges, so as to reduce production of cards.

United States Patent 1 Buchacher [451 Aug. 7, 1973 CHIPPING KNIVES FOR CHIPPING HEAD ASSEMBLIES [75] Inventor: Ernest Robert Buchacher, Langley,

British Columbia, Canada [73] Assignee: Hawker Siddeley Canada Ltd.,

Ontario, Canada [22] Filed: Aug. 3, 1971 [21] Appl. No.: 168,626

1 30] Foreign Appiication Priority Data May 11, 1971 Great Britain 14,355/71 [52] US. Cl 144/240, 144/172, 144/176 [51] Int. Cl. B27g 13/00 [58] Field of Search 144/172, 174, 176,

[56] References Cited UNITED STATES PATENTS Thompson 144/172 Forman Ottersland FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Andrew R. Juhasz Assistant Examiner-W. D. Bray Attorney-Brian .1. Wood [57] ABSTRACT A chipping knife mountable on a head rotatable about an axis at right angles to a longitudinal axis of a log to be chipped, the knife having flat bottomed grooves formed in an advance face which open into a bevelled surface so as to provide advance and trailing cutting edges, so as to reduce production of cards.

7 Claims, 3 Drawing Figures Germany 144/176 4 CHIPPING KNIVES FOR CHIPPING HEAD ASSEMBLIES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to apparatus for chipping logs to produce timber suitably dimensioned for sawing into lumber and to produce wood chips suitable for pulping. In particular the invention relates to chipping knives used in such apparatus- 2. Prior Art In production of lumber from logs less than about twenty inches in diameter it is now, generally, the practice to pass a log through a chipping assembly producing squared timber suitable for sawing into dimensioned lumber and for producing wood chips for use in pulping. Treatment of a log in this manner results in maximum use of wood, as kerf loss normally associated in operations wherein slabs are sawn from a log to provide a squared timber, is minimized.

Furthermore operational costs are reduced as production of slabs, which require further handling and processing, is eliminated.

Chipping machines used for this purpose generally incorporate a chipping head assembly having a plurality of driven chipping heads each of which carries a chipping knife, the heads rotating about axes perpendicular to the longitudinal axis of the log being chipped, the heads being disposed so that a log passed through the chipping head assembly emerges as a squared timber.

Rate of feed of the log through the chipping head assembly, and rotational speeds of the chipping heads, are adjusted to produce wood chips of suitable thickness and length for use in pulping operations. However, as the knives cut the wood longitudinally of the log grain, overwidth chips, commonly called cards, which have a width (measured across the grain) in excess of that suitable for pulping chips, are produced. The cards do not readily break up when treated in conventional tumbling apparatus and, when passed over screens prior to use in pulping operations, are usually rejected.

SUMMARY OF THE INVENTION The present invention provides a chipping knife for chipping heads of chipping assemblies, the knife materially reducing production of cards in chipping operations, providing a face which requires little or no planing to finish.

The chipping knife of the present invention has a flat advance face having alternate flat faced lands and shallow flat bottomed grooves of equal width extending across, and opening out of, a bevelled surface so as to form a plurality of alternate advance and trailing cutting edges.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an end elevation, generally diagrammatic, showing a pair of heads carrying knives engaged in chipping a log,

FIG. 2 is a detail isometric of a portion of a chipping knife,

FIG. 3 is a detail central section of a portion of the knife.

DETAILED DESCRIPTION I FIG. 1

A chipping head assembly, generally 10, has a pair of chipping heads 11 and 12 mounted on a common drive shaft 13 having an axis of rotation 14. The drive shaft is suitably powered and supported in a conventional chipping machine, not shown.

The chipping heads are, conventionally, frustoconical and carry chipping knives l5 and 15.1, the chipping knives being disposed apart. The knives have straight cutting edges 16 and 16.1 extending at a 45 angle to the shaft axis 14 so that the cut of each knife is essentially a right cone. The knives are located longitudinally of the shaft so that the cuts of inner edge corners 17and 17.1 of the cutting edges overlap. Conventional means, not shown, feed a log 18 between the heads 11 and 12 in a direction perpendicular to the axis 14 of the drive shaft, feed rate of the log being such that thickness and length of chips produced meet required standards for use in pulping.

The assembly 10 also includes a pair of chipping heads, not shown, which follow and are the same as chipping heads 11 and 12, and are disposed so as to chip the log along broken lines 21 and 21.1 so as to provide a squared timber suitable for sawing into dimensioned lumber.

FIG. 2

The chipping knife 15, which is the same as the knife 15.1, is generally rectangular in shape being about four inches in width and about onehalf inch in thickness, and has a flat advance face 22 and a flat rear face, seen only in FIG. 3 and referenced 23. Length of knife depends on diameter of logs to be chipped. Slots 24 open out of an inner side wall 25 of the knife the slots being for attachment to, and radial adjustment of, the knives on the chipping head. The knife has a double bevelled outer side wall 26.

Flat bottomed shallow rectangular sectioned grooves are machined across the advance face 22 of the knife perpendicular to the knife edge 16, width and spacing of the grooves being such as to provide alternate lands 28 and grooves 29 of equal width, the width of each land and groove being the same as that of a desired width of chip. Bottoms 29.1 of the grooves are parallel to the advance face 22 of the knife so that grooving results in the cutting edge 16 having alternate and parallel advance cutting edges 16.2 and trailing cutting edges 16.3.

FIG. 3 I j The side wall 26 of the knife is double bevelled, see also FIG. 2, having a narrow advance bevelled surface 30 bevelled at an angle 30.1 of about 39, to the advance face 22 and being aboutthree sixteenths inches in width. A trailing bevelled surface 32 extends aft from a trailing edge 31 of the advance bevelled surface 30 at a bevel angle 32.] of about 30, to the advance face. For soft woods the shallow grooves 29 are aboutthree thirty-seconds inches so that the trailing cutting edges 16.3 trail the advance cutting edges 16.2 by about one eighth inches and are about one sixteenth inches in advance of the trailing edge of the advance bevelled surface. Deeper grooves to provide up to V4 inch spacing between the advance and trailing cutting edges, and correspondingly wider advance bevelled surfaces, are required for woods of greater density.

The knife is mounted on its associated head, which rotates in a direction shown by an arrow 33, with the advance face 22 at an acute angle 34 (rake angle), about 40, to a plane 35 tangential "to a truncated cone described by the cutting edge 16 as the head 11 rotates. Thus a clearance angle 36 (angle between the advance bevelled surface 32 and the plane 35) is provided.

Provision of a clearance angle is known, its magnitude depends upon parameters as known in the art. The clearance angle 36 is such that the trailing edge of the advance bevelled surface lies on the cone of cut taken by advance edges 16.2. In a chipping knife, dimensioned as above described, clearance angle of less than 1 is provided on the advance bevelled surface 30. The clearance angle for the trailing bevelled surface 32 is less than nine degrees so as just to avoid interference with a chipped surface of the log being advanced at a required feed speed.

During operation of the chipping head assembly chips cut by the advance cutting edges start to lift ahead of chips cut by the trailing cutting edges, thus splitting the wood between adjacent chips longitudinally of the grain. Each chip thus has a width corresponding to the width of the lands and grooves. Although some of the chips cut by adjacent grooves and lands may cling together they are fractured, sufficiently to separate when tumbled in conventional tumblers or when transported in a pneumatic handling system.

Chipped faces of timber produced are smoother than lumber produced by conventional sawing thus, wood loss in planing to finished lumber is materially reduced. The chipped faces are adequately smooth for some requirements, hence planing may not be required.

The advance bevelled surface of the knives could -be frusto-conical, however, the flat bevelled surface, as shown, gives satisfactory results and, further, facilitates sharpening.

Further, configuration of chipping knives as described results in a relatively thick knife edge which is less prone to damage and has materially longer life than knives of conventional configuration.

I I claim: 7

l. A chipping knife mountable on a head rotatable about an axis at right angles to a longitudinal axis of a long to be chipped, the knife being adapted for chipping the log longitudinally of the grain, the knife comprising:

a. a flat advance face,

b. a flat rear face substantially parallel to said advance face,

c. a first outer surface extending rearwardly from said advance face at a first acute angle with respect to said advance face and defining first cutting edges at the intersection of said first outer surface and advance face,

(1. a second outer surface extending rearwardly from said first outer surface to said rear face at a second acute angle with respect to said advance face,

e. said first acute angle being greater than said second acute angle,

f. a plurality of shallow rectangular grooves formed in said advance face and having bottom surfaces substantially parallel to said advance face,

g. said bottom surfaces intersecting said first outer surface to form second cutting edges between said first cutting edges and the intersection of said first and second outer surfaces,

h. said first and second cutting edges lying in said first outer surface having the same clearance angle so as to minimize production of cards,

i. whereby said chipping knife has relatively thick cutting edges resistant to damage.

2. A chipping knife as claimed in claim 1 in which the shallow grooves are spaced apart a distance equal to their width so that said first and second cutting edges are of equal length.

3. A chipping knife as in claim 1 in which said second outer service has a bevel angle sufficient to avoid interference with a chipped surface of the log when the knife is mounted on the head so that the trailing edge of said first outer surface lies in a plane of cut of said first cutting edges.

4. A chipping knife as claimed in claim 1 in which depth of the grooves is such that said first cutting edges are spaced between one sixteenth and one quarter inches in advance of said second cutting edges.

5. A chipping knife as claimed in claim 1 in which said second cutting edges are spaced between one sixteenth inches and one eighth inches in advance of the trailing edge of said first outer surface.

6. A chipping knife as claimed in claim 3 in which said first outer surface has a clearance angle of less than l with a plane tangential to the plane of cut taken by said first cutting edges. 

1. A chipping knife mountable on a head rotatable about an axis at right angles to a longitudinal axis of a log to be chipped, the knife being adapted for chipping the log longitudinally of the grain, the knife comprising: a. a flat advance face, b. a flat rear face substantially parallel to said advance face, c. a first outer surface extending rearwardly from said advance face at a first acute angle with respect to said advance face and defining first cutting edges at the intersection of said first outer surface and advance face, d. a second outer surface extending rearwardly from said first outer surface to said rear face at a second acute angle with respect to said advance face, e. said first acute angle being greater than said second acute angle, f. a plurality of shallow rectangular grooves formed in said advance face and having bottom surfaces substantially parallel to said advance face, g. said bottom surfaces intersecting said first outer surface to form second cutting edges between said first cutting edges and the intersection of said first and second outer surfaces, h. said first and second cutting edges lying in said first outer surface having the same clearance angle so as to minimize production of cards, i. whereby said chipping knife has relatively thick cutting edges resistant to damage.
 2. A chipping knife as claimed in claim 1 in which the shallow grooves are spaced apart a distance equal to their width so that said first and second cutting edges are of equal length.
 3. A chipping knife as in claim 1 in which said second outer service has a bevel angle sufficient to avoid interference with a chipped surface of the log when the knife is mounted on the head so that the trailing edge of said first outer surface lies in a plane of cut of said first cutting edges.
 4. A chipping knife as claimed in claim 1 in which depth of the grooves is such that said first cutting edges are spaced between one sixteenth and one quarter inches in advance of said second cutting edges.
 5. A chipping knife as claimed in claim 1 in which said second cutting edges are spaced between one sixteenth inches and one eighth inches in advance of the trailing edge of said first outer surface.
 6. A chipping knife as claimed in claim 3 in which said first outer surface has a clearance angle of less than 1* with a plane tangential to the plane of cut taken by said first cutting edges.
 7. A chipping knife as claimed in claim 5 in which said first outer surface has a clearance angle of less than 1* with a plane tangential to the plane of cut taken by said first cutting edges. 